1. Technical Field
The present invention relates to a liquid-ejecting head, a liquid-ejecting apparatus, and a piezoelectric device.
2. Related Art
A liquid-ejecting head is used as a component of a liquid-ejecting apparatus and is applied to, for example, an ink jet printer. In this case, the liquid-ejecting head is used to eject a droplet of ink, and the ejected droplet then flies. Accordingly, the ink jet printer can perform printing as a result of applying the ink onto a medium such as paper.
In general, in order to eject a liquid from a nozzle, the liquid-ejecting head has an actuator that applies pressure to the liquid. Some types of actuators have a configuration in which a piezoelectric layer made of a piezoelectric material, such as crystallized piezoelectric ceramic, that exhibits an electromechanical transduction function is disposed between two electrodes. The piezoelectric layer can be deformed as a result of application of voltage through the two electrodes, and such deformation can be utilized to bring the actuator into operation, for example, in a bending vibration mode.
In the actuator having such a configuration, a common upper electrode structure is known, in which a plurality of piezoelectric layers for piezoelectric devices are formed and in which an electrode (hereinafter also referred to as an “upper electrode”) that covers the piezoelectric layers is formed so as to continuously overlie the plurality of piezoelectric devices (JP-A-2009-172878).
In the case where a piezoelectric device has a configuration in which the piezoelectric layer is disposed between a lower electrode and an upper electrode, the piezoelectric layer may have an active region and an inactive region, the active region being disposed between two electrodes, and the inactive region not being disposed between the two electrodes. In this case, in the deformation of the piezoelectric layer, strain of the active region is suppressed by the inactive region with the result that stress concentrates in the vicinity of a boundary between the active region and the inactive region.
Meanwhile, for the purpose of, for example, increasing an amount of a liquid ejected from the liquid-ejecting apparatus, the piezoelectric layer is required to be deformed in an increased amount. In the case where an amount of the deformation is increased, larger stress concentrates in the vicinity of the boundary between the active region and the inactive region, and cracking may occur, for example, in the piezoelectric layer.